NAME

smokeping_master_slave - How to run multiple distributed instances of
SmokePing

OVERVIEW

Normally smokeping probes run their tests from the host where smokeping
runs to some target host and monitor the latency of the connection
between the two.
The Master/Slave concept enables all smokeping probes to run remotely.
The use case for this is to measure the overall connectivity in a
network. If you are interested in checking that your central DNS server
or your file server works for everyone, you could setup several
smokeping instances checking up on on the two servers from multiple
locations within your network. With the Master/Slave smokeping
configuration this process becomes much simpler, as one smokeping
master server can control multiple slaves.
All monitoring data is stored and presented on the server, but
collected by the slaves. The slaves will also get their configuration
information from the master, so that you just have to maintain the
master server configuration file and the rest is taken care of
automatically.

DESCRIPTION

Architecture
The slaves communicate with the master smokeping server via the normal
smokeping web interface. On initial startup each slave connects to the
master server and asks for its assignments. When the slave has done a
round of probing it connects to the master again to deliver the
results.
If the assignment for a slave changes, the master will tell the slave
after the slave has delivered its results.
The master and the slaves sign their messages by supplying an HMAC-MD5
code (RFC 2104) of the message and a shared secret. Optionally the
whole communication can run over ssl.
[slave 1] [slave 2] [slave 3]
| | |
+-------+ | +--------+
| | |
v v v
+---------------+
| master |
+---------------+
The slave is a normal smokeping instance setup where the configuration
comes from the master instead of a local configuration file. The slave
tries to contact the master server after every round of probing,
supplying its results. If the master server can not be reached, the
results will be sent to the server together with the next round of
results. Results will be stored in a file in Perl storable form so
that they survive a restart of the smokeping instance.
MasterConfiguration
To configure a master/slave setup, add a slaves section to your
smokeping configuration file. Each slave has a section in the slaves
part of the master configuration file. The section name must match the
hostname of the slave. If some configuration parameter must be set to a
special value for the slave, use an override section to configure this.
The slave names must be the names the hosts think they have, not their
outside hostnames or ip addresses or anything like that. When the slave
calls the master to get its config or report its measurements it will
tell the master its 'hostname'. This together with the shared secret is
used to authenticate and identify who is who.
*** Slaves ***
secrets=/etc/smokeping/slavesecrets.conf
+slave1
display_name=erul22
location=India
color=ff0000
++override
Probes.FPing.binary = /usr/bin/fping
...
Then in the targets section you can define slaves at every level. Again
the settings get inherited by lower order targets and can be
overwritten anywhere in the tree.
A slave will then get the appropriate configuration assigned by the
server.
*** Targets ***
slaves = slave1 slave2
...
+dest1
slaves =
...
+dest2
slaves = slave1
...
+dest3
...
The data from the slaves will be stored in TargetName~SlaveName.rrd. So
the example above would create the following files:
dest1.rrd
dest2.rrd
dest2~slave1.rrd
dest3.rrd
dest3~slave1.rrd
dest3~slave2.rrd
The slavesecrets.conf file contains a colon separated list of hostnames
and secrets.
host1:secret1
host2:secret2
SlaveConfiguration
A smokeping slave setup has no configuration file. It just needs to
know that it runs in slave-mode and its secret. The secret is stored in
a file for optimal protection. By default the persistent data cache
will be located in /tmp/smokeping.$USER.cache.
./smokeping --master-url=http://smokeping/smokeping.cgi \
--cache-dir=/var/smokeping/ \
--shared-secret=/var/smokeping/secret.txt
The secret.txt file contains a single word, the secret of this slave.
It is NOT the same as the slavesecrets.conf file the master uses.

SECURITYCONSIDERATIONS

The master effectively has full access to slave hosts as the user
running the slave smokeping instance. The configuration is transferred
as Perl code that is evaluated on the slave. While this is done inside
a restricted "Safe" compartment, there are various ways that a
malicious master could embed arbitrary commands in the configuration
and get them to run when the slave probes its targets.
The strength of the shared secret is thus of paramount importance.
Brute forcing the secret would enable a man-in-the-middle to inject a
malicious new configuration and compromise the slave.

COPYRIGHT

LICENSE

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
675 Mass Ave, Cambridge, MA 02139, USA.